I certainly fit in that category of those with a firmly fixed preference as to side of bed. I sleep on the left side regardless: at home, on holiday, in New Zealand, overseas, in sickness, in health - and even on the double mattress above the cab in the horse-truck. If I was a hardy type who camped, I'd sleep on the left under canvas too.

I'm in good company. "Those who have a tendency to migrate to the left of a double bed are apparently happier than their 'right' counterparts," said the Daily Mail report. A study of 3000 adults found that "more than a quarter of people who snooze on the left side of the bed feel they have a really positive outlook on life in general, compared to 18 per cent of right-side sleepers."

While the original article didn't clarify which left they were referring to, I assume it's the side as perceived by the occupant of the bed while sitting up against the pillows. When I say I sleep on the left that's the left from my perspective when I'm in bed. Surely that's obvious? I don't think many people would talk about the side as if they're observing the bed from across the room.

Various theories are bandied about to explain why some of us have such ingrained sleeping preferences. The caveman theory says that the man in the relationship should sleep on the side nearest the door so he can protect his female partner from intruders. That's a chivalrous take on the subject but intruders could also get in through a window which is often on the opposite side to the door so I'm not convinced by that argument. Also it breaks down completely in the case of same-sex couples.

The theory about handedness - that says left-handed people sleep on the left and right-handed on the right so it's easy to reach objects on the bedside table - is spurious, too, while the convenience theory which decrees that the person with the weakest bladder should sleep on the side nearest the bathroom has an appealing pragmatism.

Without citing reasons, Feng Shui for Romantic Marriages - Most Frequently Asked Questions says, "The woman should sleep on the right side (as you lie in the bed), and the man should sleep on the left." This is the same website that recommends placing a conch shell in the bedroom to guard against infidelity which surely casts doubt on its credibility.

Considering this issue has made me suddenly aware that my husband's side of the bed has the master electrical control panel beside it. While I can only switch my bedside light on and off, he has additional dimming privileges and the ability to control the overhead fan. Perhaps what I'd always interpreted as dull married habit is in fact a misogynistic power play designed to seize control on behalf of the patriarchy. Awkward.

Which side of the bed do you sleep on? And why do you think that might be? Are you flexible about it or is your preference set in stone?

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Shelley Bridgeman is a truck-driving, supermarket-going, horse-riding mother-of-one who is still married to her first husband. As a Herald online blogger, she specialises in First World Problems and delves fearlessly into the minutiae of daily life. Twice a week, she shares her perspective on a pressing current issue and invites readers to add their ten cents’ worth to the debate.